A current trend in the telecommunications industry utilizes a decomposed voice over packet architecture in which a call control functionality is performed by one element and the actual bearing of data is accomplished by a second element. Prior to this decomposition technique, call control and call bearing were performed by one element, and the way that element worked was proprietary and unique to each telecommunications provider. Now, there are industry-wide standards, the call control element has been separated (logically, and in some cases physically as well) from the call bearing element, and telecommunications providers can work together to devise solutions to satisfy the constant demand on the telecommunications industry to provide faster and more complex services.
A media gateway is a network element that provides conversion between media (voice, video, data, etc.) and data packets carried over a core packet (IP, ATM, etc.) network. A media gateway supports a collection of endpoints. An endpoint sources and/or sinks one or more media streams.
In a conventional decomposed voice over packet architecture, an external call control element typically establishes a call between two endpoints on different media gateways via the core packet network. The call control element is logically external to the media gateway, while it may or may not reside in the same physical box or location. The external call control element is typically unaware of any possible connection between two endpoints other than the core packet network. It is possible that the two endpoints reside within the same network device or within different network devices that are in close proximity to one another. Alternative connections between endpoints are called alternate bearer possibilities, and may include such connections as ATM, virtual channel or TDM networks, pre-resolved IP paths, MPLS or VLAN networks or pseudo-wires, among others. In a decomposed voice over packet architecture, the external call control element is typically unaware of these alternate bearer possibilities.
In the prior art, however, it is known for the external call control element to discern that if a call originates and terminates on the same media gateway, there is a bearer possibility other than the core packet network. Media gateway control protocols including Media Gateway Control Protocol (MGCP), Trunking Gateway Control Protocol (TGCP), Network-based Call Signaling (NCS), Megaco/H.248 and SIP define syntax and semantics which allow the external call control element to specify an alternate bearer possibility when a call originates and terminates on the same media gateway. However, these constructs cannot be used in conjunction with endpoints which reside on different media gateways.